Coaxial switch having means to reflectionlessly terminate disconnected branches



y 5, 1964 A. J. WOZNIAK 3,132,311

COAXIAL SWITCH HAVING MEANS TO REFLECTIONLESSLY TERMINATE DISCONNECTEDBRANCHES Filed Jan. 27, 1960 7 M W W United States Patent M 3,132,311COAXIAL SWETCH HAVING MEANS T0 REFLEC- TIONLESSLY T E R M I N A T EDISCONNECTED BRANCHES Adolph J. Wozniak, Bay Village, Ohio, assignor toThompson Ramo Wooldridge Inc, Cleveland,

Ohio, a corporation of Ohio Filed Jan. 27, 1960, Ser. No. 4,961 3Claims. (Cl. 333-7) This invention relates to a radio frequency switchand particularly to a switch for coaxial lines wherein unused lines areterminated in their characteristic impedance by means of the switch.

In various switching applications it is important for unused linesconnected to a switch to be terminated in their characteristicimpedance. The present invention provides an extremely simple andeffective means for terminating unused lines connected with a coaxialswitch in a desired mpedance. In accordance with a preferred embodimentof the invention, the rotor is provided with a pocket opposite an unusedterminal of the switch which receives an insulating medium having acarbon film sprayed thereon. A conductive band overlying the outerperiphery of the carbon film makes contact with the outer conductor ofthe unused terminal and an inner conductive band overlying the innerportion of the carbon film makes contact with the inner conductor of theunused terminal. Preferably, the inner conductive band is connected tothe inner conductor of the unused terminal by means of a buttonreoiprocably carried by the insulating material and urged into contactwith the inner conductor by means of a conductive spring washerinterposed between the head of the button and the inner conductive bandon the carbon film.

It is therefore an important object of the present invention to providea novel and extremely simple means for terminating unused terminals of acoaxial switch in their characteristic impedance.

Another object of the invention is to provide a resistance terminationtor unused terminals of a coaxial switch which is readily applied toexisting switches.

A further object of the present invention is to provide a resistancetermination for unused terminals of a switch which is of a precise andstable predetermined value.

Other objects, features and advantages of the present invention will beapparent from the following detailed description taken in connectionwith the accompanying drawings, in which:

FIGURE 1 is a somewhat diagrammatic longitudinal sectional view of acommercial coaxial switch to which an embodiment of the presentinvention has been applied;

FIGURE 2 is an enlarged fragmentary view partly in section andillustrating a terminating element associated with a coaxial switchrotor in accordance with the present invention.

As shown on the drawings:

FIGURE 1 illustrates a commercially avail-able coaxial switch to whichthe teachings of the present invention have been applied. The switchcomprises a series of radially extending terminals such as indicated at10 and 11 'for threadedly receiving coaxial lines which are to beselectively connected with an axial terminal 12 of the coaxial switch14. The switch 14 may comprise a housing 15 of electrically conductivematerial having a central rotor chamber 16, a series of radial passagessuch as 17 and 18 opening into the rotor chamber 16 and an axial passage"19 opening into the rotor chamber. The terminals 10, 11 and 12 may beexternally threaded as indicated at 22, 23 and 24 to receive suitablecouplings of the coaxial lines associated with the switch. Continuity isthus provided between the outer conductors of the 3,132,311 Patented May5, 1964 respective coaxial lines and the interior walls of the pas sages17, 18 and '19, which in eflect provide extensions of the coaxial lineswithin the housing. The terminals may have suitable insulating sleevessuch as indicated at 27, 28 and 29 mounting inner conductors 32, 33 and34, whose outer ends are suitably configured to be coupled with theinner conductors of the coaxial lines connected with the terminals. Byway of example, the outer ends of the inner conductors may have reduceddiameter bores extending axially therein from their outer ends forreceiving reduced diameter pins on the ends of the inner conductors ofthe coaxial lines connected with the terminals to provide firmelectrical continuity between the inner conductors of the lines and theinner conductors of the respective terminals. Generally speaking, theterminals provide coaxial line sections having the same characteristicimpedance as the coaxial lines to be connected with the terminals.

The rotor 40 of the coaxial switch comprises a substan tiallycylindrical body portion of electrically conductive material fittingsnugly within the rotor chamber 16 so that the walls of the housing 15defining the motor chamber 16 are in electrical continuity with theouter walls of the rotor 40. The rotor, in the illustrated embodiment,is provided with a curved interior passage .2 of configuration toregister with one of the terminals such as 10 and 11 and to electricallyconnect the line associated with such terminal with the line connectedto the terminal 12. The passage 42 has a curved inner conductor member45 mounted therein by means of a curved insulating sleeve 47, so thatthe respective ends of the inner conductor member 45 are adapted forelectrical continuity with the inner end of the axial inner conductor 34of terminal 12 and selectively with the inner ends of the radial innerconductors 32 and 33 of terminals 10 andfll, for example. In theposition shown in FIGURE 1, terminal 11 is connected with terminal 12 bymeans of the rotor coaxial line section including the outer conductorformed by passage 42 and the inner conductor formed by curved member 45.By way of example, there may be six radial terminals such .as 10 and 11,so that a different radial terminal is connected with the axial terminal12 for each 60 degrees of rotation of the rotor 40. When rotor 40 isrotated through conductor 45 is in electrical continuity with the innerend of inner conductor 32 of terminal 10 and terminal 10 is electricallyconnected with terminal 12 by means of the rotor coaxial line section.

A spring washer is indicated at 50 interposed between the lower end faceof the rotor body and a cover member 55 for urging the rotor 40 axiallyagainst theopposite end wall of the housing. This spring washer 50 mayserve to provide firm electrical contact between the inner conductor 34of terminal 12 and the adjacent end of rotor inner conductor 45, as wellas providing firm electrical continuity between the rotor axial end faceand the adjacent wall of the rotor chamber 16.

In the illustrated embodiment the radial passages such as 17 and 18 andaxial passage 19 may be cylindrical and of the same diameter as theinterior diameter of the outer conductors of the lines with which theyare connected. Similarly the inner conductors such as 32, 33 and 34 maybe of cylindrical cross section and have the same outside diameter asthe outside diameter of the inner conductors of the lines with which theterminals are connected. The rotor conductor 45 may be cylindrical incross section-and of the same external diameter as'the inner conductors32, 33 and 34, and the rotor passage 42 may be of circular cross sectionand dimensioned so as to providea continuation of the switch terminalsintroducing minimum electrical discontinuities.

While, within the scope of the present invention, the coaxial switchrotor 40 may be manually actuated beeen successive switching positions,for example by means such as illustrated in the Gates U.S. Patent No.2,745,917, issued May 15, 1956, an electrically energized actuatingsystem has actually been diagrammatically shown in FIGURE 1 similar-tthat shown in Schunemann and Thoren US. Patent No. 2,840,786, issuedJune 24, 1958. The details of this actuating system are not material tothe description of the present invention, but it may be noted generallythat the actuating mechanism is enclosed within a casing 60 sealed tothe cover plate 55. The cover plate 55 may be secured to the switchhousing 15 by suitable screws. An electric control cable may beconnected to the actuating mechanism by means of the fitting 61 sealedto the casing 60 and including electrical conductors 63, 64 and 65 forconnection with corresponding conductors of the electric control cable.The actuating mechanism itself comprises a rotary type solenoid 70 whichis coupled to the shaft 71 of the rotor 40 by suitable clutch means 73and 74. Suitable electric indexing switch means is generally indicatedat 75. Detent means is indicated at 76 for precisely positioning therotor 40 in each of its switching positions and may comprise a detentwheel 78 fixed to the rotor shaft 71 and cooperating spring urged detentarms such as indicated at 80. For a six position coaxial switch, therewould be six pins such as 63 and 65 in addition to a center pin such as64 associated with the fitting 61, so as to actuate the switch to any ofsix selected positions under the control of the indexing mechanismindicated generally at 75. In operation, it will be understood that therotary solenoid 70 may be successively energized to move the rotor 40between successive detent positions. By way of example, detent wheel 78may have 12 stable positions, so that the solenoid 70 is actuated twiceto step the rotor between adjacent switching positions, where a total ofsix switching positions are provided.

In accordance with the present invention, one or more of the unusedterminals such as terminal in FIGURE 1 is terminated in itscharacteristic impedance by means of a resistance element designatedgenerally by the reference numeral 90 and shown in detail in FIGURE 2.As seen in FIGURE 2 the rotor 40 includes cylindrical surface portions40a and 40b engaging the adjacent wall of the rotor chamber 16. Atlocations about the periphery of the rotor corresponding to unusedterminals, the rotor 40 is provided with cylindrical recesses such asindicated at 400. The recesses 400 are defined by cylindrical walls 40dof diameter substantially corresponding to the diameter of the outerconductors such as 17 of the terminals such as [10 in FIGURE 1. Therecess 400 is also provided with an annular end wall 402 which may havea circular area in a single plane, but it is shown broken by a reduceddiameter recessed portion 40). In the illustrated embodiment, the recess40f serves to insulate the end of the shaft portion 93 of contact button95 from the rotor 40. The recess 40) enables the shaft 93 to be ofgreater length than the axial dimension of annular supporting member 97when desired.

The supporting member 97 may be of suitable dielectric material fittingsnugly within the recess 40c with its cylindrical outer periphery 97a inengagement with the cylindrical Wall 40d and with its axial end face 97bin snug engagement with the annular wall 40e of the rotor. In thepreferred embodiment, the annulus 97 has a coating or film of carbonresistive material 99 sprayed thereon. At the outer perimeter 99a of thefilm 99 a conductive band 101 is provided which may include a portion101g of annular or ring configuration overlying the film portlon 99c andan axially extending portion 101b in firm electrical contact with thewall 40d of recess 400 in the rotor 40. The band or ring 101 may be ofsilver or other highly conductive material and constitutes one ternnnalof the resistance element. The band 101 is electrically connected withthe outer conductor of the unused 4 terminal with which the terminatingelement is registered.

Centrally of the terminating element 90, member 97 is provided as acentral cylindrical aperture 104 and the film 99 is similarly apertured.Surrounding the aperture in the film at an inner peripheral portion 99bof the film is provided a conductive band or ring 110 of silver whichoverlies the portion 99b of the resistive film 99 and forms an innerterminal for the film. The film 99 may, for example, provide :aresistance equal to the characteristic impedance of the terminals suchas 10 and 1 1 between its inner and outer terminals 110 and 101. Contactbutton has its head 112 disposed for engagement with the inner conductorsuch as 32 of the unused terminal and a suitable spring washer such asindicated at 114 has its outer periphery 11411 in electrical contactwith the conductive band 114 and its inner portion in engagement withthe underside of the head 112 to provide a firm electrical connectionbetween the button 95 and the terminal of the resistance film 99. Theshaft 93 may fit snugly in the bore 104 so as to be guided for axialmovement under the urging of the spring member 114.

As indicated in FIGURE 2, with the spring 114 in normal untensionedposition, the outer surface 1120 of the head 112 of button 95 isradially outward of the surfaces such as indicated at 40:: and 40b ofthe rotor 40. When the rotor 40 is assembled within the rotor chamber,however, the button is depressed tensioning the spring 114 until thesurface 112a is substantially flush with the surfaces such as indicatedat 40a and 40b of the rotor 40. The head 112 of the contact button 95 isof substantially the same diameter as the inner conductors such as 32and is of a diameter greater than the difference in radius between airmatch sections such as 18a of terminal 11 and the outer radius of theinner conductor 33 of the terminal, so as to slide smoothly from contactwith the cylindrical wall of the rotor chamber 16 into contact with theinner ends of the inner concluctors such as 32 and 33 of the terminals.The diameter of the head 112 is less than the diameter of the air matchsection such as 18a, so that the spring 114 is operative to resilientlypress the head 112 directly against the inner end of the innerconductors such as 32 and 33 free of the adjacent wall portions of therotor chamber 16. The button 95 and the spring 114 may be of a suitablehighly electrically conductive material.

The silver band 101 is preferably applied to the outer perimeter 99a ofthe carbon film 99 after the member 97 with the film sprayed thereon isinserted in the rotor recess 40c in order that the band 101 may makesecure electrical contact with the walls such as 40d of the rotorrecess. The silver forming the band 101 may be applied in a molten stateso as to actually be fused with the film 99 and with the side wall 40dof the rotor recess. In this event, not only is excellent electricalcontact provided, but the band 101 serves to assist in retaining themember 97 in the recess 400.

It will be apparent that many modifications and variations may beeifectcd without departing from the scope of the novel concepts of thepresent invention.

1 claim as my invention:

1. A coaxial switch comprising a housing with an interior rotor chamberand a series of coaxial line terminals opening into said chamber, and arotor in said rotor chamber and having a coaxial line section forinterconnecting selective ones of said terminals, said rotor having anelectrical impedance element carried at the periphery thereof forregistration with at least one of said coaxial line terminals to providea termination for said one terminal in one position of said rotor, saidimpedance element comprising an annulus of electrically resistivematerial having a central aperture, and an inner conductor contactbutton having a shaft portion extending through said aperture, meanselectrically connecting said contact button with the inner perimeter ofsaid annulus of electrically resistive material, and means forresiliently pressing said button into contact with the inner conductorof the terminal with which it is registered.

2. A coaxial switch comprising a housing with an interior rotor chamberand a series of coaxial line terminals including inner and outerconductors opening into said chamber, a rotor in said rotor chamberhaving a coaxial line section including inner and outer conductors forinterconnecting selected ones of said terminals, said rotor having arecess in the periphery thereof for registration with one of saidterminals in a predetermined position of the rotor, and a resistiveelement comprising an insulating member in said recess, a film ofresistive material on said insulating member, outer and inner conductivebands overlying an outer peripheral portion and an inner peripheralportion of said film in electrical contact therewith, and meansproviding for electrical continuity between said outer conductive bandand the outer conductor of said one terminal and between said innerconductive band and the inner conductor of said one terminal when theterminal is aligned therewith.

3. A coaxial switch comprising a housing with an interior rotor chamberand a series of coaxial line terminals,

including inner and outer conductors opening into said chamber, a rotorin said rotor chamber and having a coaxial line section forinterconnecting selected ones of 6 said terminals, said rotor having arecess in the periphery thereof, and a resistive element in said recessand carried by said rotor comprising an insulating material having afilm of resistive material at the outer surface thereof for alignmentwith one of the terminals of said housing in apredetermined position ofsaid rotor, means providing electrical continuity between an outerperipheral portion of said film and the outer conductor of the terminal,said film having a central aperture and having a conductive bandsurrounding said aperture, an electrically conductive button having ashaft portion extending through said aperture and a head portion forcontact with the inner conductor of said one terminal, and an annularspring interposed between said inner band and said head for resilientlyurging said head into contact with the inner conductor of the terminalwhen the rotor is in said predetermined position.

References Cited in the file of this patent UNITED STATES PATENTS2,344,780 Kram Mar. 21, 1944 2,473,565 Bird June 21, 1949 2,629,048 DykeFeb. 17, 1953 2,782,377 Selby Feb. 19, 1957 2,840,786 Schunemann et alJune 24, 1958 2,958,054 Concelman Oct. 25, 1960

1. A COAXIAL SWITCH COMPRISING A HOUSING WITH AN INTERIOR ROTOR CHAMBERAND A SERIES OF COAXIAL LINE TERMINALS OPENING INTO SAID CHAMBER, AND AROTOR IN SAID ROTOR CHAMBER AND HAVING A COAXIAL LINE SECTION FORINTERCONNECTING SELECTIVE ONES OF SAID TERMINALS, SAID ROTOR HAVING ANELECTRICAL IMPEDANCE ELEMENT CARRIED AT THE PERIPHERY THEREOF FORREGISTRATION WITH AT LEAST ONE OF SAID COAXIAL LINE TERMINALS TO PROVIDEA TERMINATION FOR SAID ONE TERMINAL IN ONE POSITION OF SAID ROTOR, SAIDIMPEDANCE ELEMENT COMPRISING AN ANNULUS OF ELECTRICALLY RESISTIVEMATERIAL HAVING A CENTRAL APERTURE, AND AN INNER CONDUCTOR CONTACTBUTTON HAVING A SHAFT PORTION EXTENDING THROUGH SAID APERTURE, MEANSELECTRICALLY CONNECTING SAID CONTACT BUTTON WITH THE INNER PERIMETER OFSAID ANNULUS OF ELECTRICALLY RESISTIVE MATERIAL, AND MEANS FORRESILIENTLY PRESSING SAID BUTTON INTO CONTACT WITH THE INNER CONDUCTOROF THE TERMINAL WITH WHICH IT IS REGISTERED.